Desa H) AND VM42EP(B, VM36EP Troubleshooting, Observed Problem Possible Cause, Remedy

Models: M36EP

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Note: Before troubleshooting the system, make sure the gas shutoff valve is ON. The two most common causes of a malfunctioning gas appliance are:

1.Loose wiring connections

2.Construction debris clogging the pilot and/or gas control valve filter



Ignitor will not spark or pilot will not light

1.No gas supply or shutoff valve is OFF

2.Air in gas line

3.Construction debris clog- ging pilot orifice

4.Low gas pressure

5.Kinked pilot line

6.Control valve knob is not opening

7.No power to unit or the ignition module or power transformer is bad

8. Vent damper not fully open

1.Check to see if you have gas supply and that equipment shutoff valve is opened

2.Repeat lighting procedure sev- eral times to purge all air out of lines. If after repeated attempts appliance does not light, call for qualified service and repair.

3.Remove debris and dirt, in- spect and clean any other possible obstructions

4.Contact your gas supplier to check pressure

5.Have a qualified technician replace pilot line

6.Replace control valve (Refer to Replacement Parts, page 20)

7.Check that main power is on and that all wire connections are made correctly to the ignition model (see Wiring Diagram, page 21). Check for 24 VAC at the secondary side of the transformer. If 24 VAC is present and the module does not operate, have the module replaced otherwise have the transformer replaced

8.Open vent damper until fully locked in OPEN position

Pilot will not stay lit


Loose wiring on ignitor wire



to ignition module and/or poor



ground to ignition module



Pilot flame too low to sense

1.Check wiring connection. Refer to wiring diagram (see Wiring Diagram, page 21) and/or check ground wire to ignition module

2.Clean and adjust pilot burner and check gas supply and inlet

pressure to unit

Note: Have a qualified technician replace pilot assembly if broken or corroded

No gas to burner, although wall


Wall switch wires defective or


Check electrical connections

switch and valve are set to the


too long


Recheck problems 1 and 2

ON position


Thermopile not generating



sufficient voltage





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Desa H) AND VM42EP(B, VM36EP installation manual Troubleshooting, Observed Problem Possible Cause, Remedy